Spatial coding is a prominent aspect of sensory processing in a number of sensory systems. It forms an important basis for sight, hearing, and feeling, and can provide important, distinctive clues to dysfunction in these senses. The proposed program of research seeks to understand the significance of spatial coding in the function and structure of the olfactory system by examining how spatial factors are represented in and influence the organization of olfactory receptor neurons. The overall analysis will be keyed to an organizational framework for olfactory spatial coding known as rhinotopy, which is the way that sensory space within the nose is mapped onto the olfactory bulb. The overall goal of the present research program is to examine the hypothesis that rhinotopy is an inherent organizational principle in the olfactory system which represents the separate, but parallel processing of high and low resolution information about odorant molecules. The principal short-term goal is to demonstrate that the projections of the olfactory receptor neurons in the nose to the mitral and tufted cells of the olfactory bulb are more highly convergent in some rhinotopically distinct zones than in others. This would provide evidence for zonal variation in the anatomical receptive fields of mitral and tufted cells that would be consistent with a hypothesis for zonal differences in stimulus resolving power. The second short-term goal is to offer evidence that rhinotopic patterning (in ORN-to-MOB convergence ratios, activity of the metabolic enzyme NADPH diaphorase, and basal cell proliferation) is maintained in the face of perturbations in airflow and sensory stimulation following perinatal naris occlusion. This finding would be consistent with the notion that rhinotopy is an inherent characteristic of the biological design of the olfactory system that does not depend upon significant periods of early sensory stimulation for its expression. The results should proide a means to understand how spatial mapping is used in the olfactory system, and the extent to which rhinotopy guides the functioning, development and persistent renewal of the primary olfactory pathways. The findings should help to identify important strategies for studying the role of spatial coding in the human nose and in human olfactory dysfunction.